Hi
I have a 2001 330i with about 85k miles. The car was fine yesterday. This morning the battery was totally dead. I assumed that the battery just gave up the ghost without warning and bought a new one (probably a mistake). After putting in the replacement battery the radiator fan came on full blast. Even before the car started. I didn't really notice it at first since I was at the back fooling around with the battery. But after driving it around for a couple of hours it was obvious that there is something wrong with the fan, or a switch or a thermostat or some wiring. The fan is running full speed all the time even when the car is turned off.
I eventually just unplugged the fan from the electrical system and am trying to figure out what has actually gone wrong so I can replace the appropriate part.
Any suggestions on how to troubleshoot and locate whatever the offending component is? Now that I think about it, its probably not the thermostat since that is a mechanical piece.
Hoping to avoid having to bring the car into the shop so they can troubleshoot it.
Thanks, Derek
IIRC the fan is controlled by a gizmo mounted in the engine bay, not directly by the thermostat/switch. So I'd suspect and investigate the fan controller.
Another way to do this is to follow the fan power back to ... whatever it takes you to... and verify that item is properly functioning.
Some use of the Search function, and a report on your findings and results, would be useful. You have to help yourself; although it's okay to ask questions you're expected to be informed of the system you're having issues with. With the depth of knowledge already posted, some research can show you the way and keep the post count down. Resulting in a more satisfied owner.
Charlie
Your mission, should you decide to accept it, is to add value to these threads, either by pictures or by descriptions, so the next person with the same or similar problem stands on your shoulders.
The fan has power at all times. It's controlled by the engine computer (DME in BMWeze). The "box" on top of the fan has nothing to do with the fan. It's called the "AUC" and it samples the air for pollution. There is an electronic box in the fan. This "interprets" the speed commands from the DME into voltages for the fan motor. This results in various fan speeds.
Read this to get a better understanding of what's happening.
https://drive.google.com/file/d/0B59...VlE/view?pli=1
The fan does not have power with key off.
There are two relays, one is for the DME, the other is for a/c. They are in the ebox, but I have never had to look for them.
usually just a relay going bad and sticking closed when they key is off.
Last edited by Onizukachan; 06-10-2017 at 05:10 AM.
If I were to give my Touring a first name, I'd probably name it "Alan".
Mostly because I like puns.
Mutual Admiration Society #5
The fan has power at all times. Why? So the DME can command the fan to run if conditions require it to be run.
Last edited by Eaglesail; 06-10-2017 at 03:38 PM.
I cant imagine why there should be any major amp-draw dc component (such as the cooling fan) on any car remaining active after the key ignition is switched off. This could be downright dangerous with a garaged car....or in any event!
The reason why the efan can be on after the ignition is off is too cool the engine when the driver has shut off the engine after a hot run. The DME uses data from several sensors, including both coolant temperature sensors to determine when the fan needs to run.
OP, it's likely that your fan's electronics are toast. That's why I gave you the link to BMW-NORTH's document on fan's.
Well I just pulled everything apart and looked at it all very closely.
The fan is definitely getting power with the ignition off. Based on what I've seen I think this is normal.
I disassembled the fan as far as I could go without ruining it. It looks like the electronics module is not made to be replaced independently of the fan. In the document that Marco supplied it specifically calls out the failure mode that I'm experiencing. The doc chalks it up to a bad fan control module.
If there is some way to find a new replacement of the fan control module itself let me know. I'm handy enough with a soldering iron to replace the module. Otherwise I guess I have to get a whole new fan. Which is probably beaucoup bucks.
Looks like the BMW unit is about $500. The other ones are about half that price.
Does anyone have knowledge of how reliable the aftermarket fans are? The original unit lasted 16 years, which isn't too shabby I guess.
I have a used but good oem fan.
If I were to give my Touring a first name, I'd probably name it "Alan".
Mostly because I like puns.
Mutual Admiration Society #5
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